JPH09308294A - Stepping motor derive control apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize drive control of a stepping motor which is optimized for application environment in a stepping motor drive control apparatus for driving and controlling a stepping motor which is driven as an engine control means. SOLUTION: A stepping motor drive control apparatus for driving and controlling a stepping motor 26 to drive a flow rate control valve 23 comprises a battery sensor 45 for detecting a battery voltage BAT of a battery 46, a water temperature sensor 13 for detecting a cooling water temperature THW, a driving direction judging means for judging the driving direction of the stepping motor 26 and a drive frequency setting means for setting the upper limit value of the stepping motor drive frequency depending on the detected battery voltage BAT and cooling water temperature THW. The drive frequency setting means sets, when the stepping motor 26 is driven is the load reducing direction, the upper limit value of the stepping motor drive frequency to a large value and sets, when the stepping motor is driven in the load increasing direction, the upper limit value of the stepping motor drive frequency to the value lower than that when the stepping motor is driven in the load reducing direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a step motor drive control device, and more particularly to a step motor drive control device for driving and controlling a step motor driven as engine control means.

[0002]

2. Description of the Related Art Generally, step motors are diversified as actuators of various control devices for controlling an engine. For example, Japanese Patent Application Laid-Open No. 61-19946 discloses an engine throttle control device that drives a step motor to electrically control the throttle of the engine.

This throttle control device is constructed so that the throttle is driven by a step motor. Then, the depression amount of the accelerator pedal is converted into an electric signal by the accelerator sensor, and the step motor is driven according to the output signal from the accelerator sensor to open and close the throttle according to the depression amount of the accelerator pedal. Has been done.

This stepping motor has a rotor inside, and is configured to rotate the rotor by switching excitation to a plurality of magnetic poles arranged around the rotor. Specifically, the step motor drive control device supplies a drive pulse current to the stepping motor to control the rotation amount of the rotor.

By the way, when the voltage of the power supply unit which is the drive source of the step motor drops to a value that reduces the output torque of the step motor, the step motor drive controller supplies a drive pulse signal of high frequency. Then, the step motor cannot be driven following the high frequency drive pulse signal, and a so-called step-out phenomenon occurs. When this step-out phenomenon occurs, it becomes impossible to drive the throttle corresponding to the depression amount of the accelerator pedal, and the control accuracy is deteriorated.

Therefore, in the above-mentioned throttle control device, the upper limit value of the drive frequency for driving the step motor is calculated according to the voltage of the power source section, and the step motor is operated in the frequency range up to the calculated upper limit value of the drive frequency. The drive pulse signal is supplied to prevent the occurrence of the step-out phenomenon.

[0007]

In the throttle control device configured as described above, the upper limit value of the drive frequency is uniformly determined with respect to the power supply voltage. However,
A force (hereinafter, this force is referred to as a resistance force) acts on the step motor to prevent its driving.

Specifically, the grease provided for lubrication in the step motor has a low viscosity at a high temperature and does not have a resistance force, but has a high viscosity at a low temperature. And acts to prevent the rotation of the step motor rotor. Further, the resistance force may be generated depending on the usage state of the step motor. For example, in the example of the throttle control device described above, the throttle is normally biased in the valve closing direction by a spring or the like from the point of fail-safe. Therefore, when opening the throttle, the step motor must open the throttle against the elastic force of the spring. In this case, the elastic force of the spring acts as a resistance force on the step motor. On the contrary, when the throttle valve is closed, the elastic force of the spring acts in a direction to help drive the step motor. As described above, depending on the usage state of the step motor, the resistance force may change depending on the rotation direction of the step motor.

Therefore, even if the power supply voltage is constant, if a resistance force is generated due to factors such as temperature conditions and the direction of rotation, the rotation of the rotor may be restricted by this resistance force and a step-out phenomenon may occur. Therefore, even if the power supply voltage is in the same voltage state, the optimum upper limit value of the drive frequency differs depending on the temperature state, and the allowable upper limit value of the drive frequency differs depending on the rotation direction. Specifically, when the resistance force is large, it is necessary to set the upper limit value of the drive frequency of the step motor to be small.

On the other hand, as described above, since the upper limit value of the drive frequency is conventionally determined only by the voltage, when the upper limit value of the drive frequency is set high, the temperature is low or the step motor has a resistance force. In the state where the step motor is rotating in the direction in which is applied, the step motor cannot be driven following the high drive frequency, and step-out may occur.

If the upper limit of the driving frequency is set low to cope with this, the temperature rises as the step motor is used, and the resistance is not applied due to reverse rotation of the step motor. When rotated to
The upper limit value set to the upper limit value of the allowable drive frequency becomes small, the drive response of the step motor deteriorates,
There is a problem that controllability may be deteriorated.

The present invention has been made in view of the above-mentioned points, and in addition to the voltage state, the upper limit value of the driving frequency of the step motor is set on the basis of the temperature state and the rotating direction, so that the operating environment state is set. It is an object of the present invention to provide a step motor drive control device that can realize the step motor drive control optimized to the above.

[0013]

The above objects can be attained by taking the following means. Claim 1
In the described invention, in the step motor drive control device for driving and controlling the step motor driven as the engine control means, voltage detection means for detecting the voltage of the drive power supply,
It is characterized by comprising temperature detection means for detecting a temperature state, and drive frequency setting means for setting an upper limit value of the step motor drive frequency based on the detection results of the voltage detection means and the temperature detection means. is there.

According to another aspect of the present invention, in a step motor drive control device for driving and controlling a step motor driven as engine control means, a voltage detection means for detecting a voltage of a drive power supply and a temperature for detecting a temperature state. Based on the detection means, the drive direction determination means for determining the drive direction of the step motor, the voltage value and the temperature value, the step motor drive frequency of the step motor when the step motor is driven in the direction in which the drive resistance is small. A first drive frequency setting means for obtaining and setting an upper limit value, and an upper limit value for the step motor drive frequency when the step motor is driven in a direction in which the drive resistance is large is obtained based on the voltage value and the temperature value. The first drive frequency setting means sets the second drive frequency setting means based on the detection result of the second drive frequency setting means and the drive direction determining means. Boss was the upper limit, or is characterized in that said second drive frequency setting means comprises a selection means for selecting an upper limit value set.

Further, in the invention according to claim 3, in a step motor drive control device for controlling the amount of fuel supplied to the engine by the drive amount of the step motor, voltage detecting means for detecting a battery voltage and temperature of the engine. It is characterized by comprising temperature detecting means for detecting a state and drive frequency setting means for setting an upper limit value of the step motor drive frequency based on the detection results of the voltage detecting means and the temperature detecting means. .

Further, in the invention according to claim 4, in the step motor drive control device for controlling the fuel amount supplied to the engine by the drive amount of the step motor, the voltage detecting means for detecting the battery voltage and the temperature condition of the engine. Temperature detection means for detecting the drive direction of the step motor, drive direction determination means for determining the drive direction of the step motor, drive frequency for setting the upper limit of the step motor drive frequency based on the detection results of the voltage detection means and the temperature detection means. And a drive frequency setting means, the drive frequency setting means, based on the determination result of the drive direction determination means, when the step motor is driven in a load reducing direction with a small drive resistance, the upper limit of the step motor drive frequency. When the step motor is driven in the increasing load direction with a large driving resistance while setting a large value, It is characterized in that the smaller is than the upper limit of Teppumota the drive frequency when the drive to the load down direction.

Each of the above means operates as follows.
According to the invention described in claims 1 and 3, the voltage detecting means detects the voltage of the driving power source (battery voltage), and the temperature detecting means detects the temperature state of the step motor. The drive frequency setting means sets the upper limit value of the step motor drive frequency based on the detection results of the voltage detecting means and the temperature detecting means.

Therefore, it becomes possible to set the upper limit value of the driving frequency of the step motor to an optimum value according to the voltage and the temperature condition, and the upper limit of the driving frequency adapted to the low temperature with a large resistance force and the high temperature with a small resistance force. It is possible to set the value. As a result, when driving the step motor,
It is possible to effectively prevent the occurrence of step-out and perform drive control with good responsiveness.

According to the second and fourth aspects of the invention, the voltage detecting means detects the voltage (battery voltage) of the driving power source, the temperature detecting means detects the temperature state of the step motor, and further the driving direction determination. The means determines the driving direction of the step motor. The drive frequency setting means sets the upper limit value of the step motor drive frequency based on the detection results of the voltage detecting means and the temperature detecting means.

Further, the driving frequency setting means or the selecting means sets the upper limit value of the stepping motor driving frequency when the stepping motor is driven in the unloading direction with a small driving resistance based on the judgment result of the driving direction judging means. Set larger. On the contrary, when the step motor is driven in the increasing load direction in which the driving resistance is large, the upper limit value of the step motor driving frequency is set smaller than that in the driving in the decreasing load direction.

As a result, in addition to the operation of the invention described in claims 1 and 2, it becomes possible to optimize the upper limit value of the drive frequency according to the rotation direction of the step motor.
Therefore, it is possible to improve the responsiveness when the step motor rotates in the load reducing direction, and it is possible to prevent the occurrence of step-out when the step motor rotates in the load increasing direction.

Further, when the above step motor drive control device is applied to the fuel supply system of the engine as in the inventions of claims 3 and 4, step-out of the step motor is prevented and the response is improved. Therefore, the increase / decrease control of the fuel supply can be performed promptly and with high accuracy, and the reliability of engine control can be improved.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a system configuration diagram of a gas fuel internal combustion engine (hereinafter simply referred to as an LPG engine) to which a step motor drive control device according to an embodiment of the present invention is applied. LPG engine 1 is liquefied petroleum gas (LPG)
Is used as fuel, and is roughly composed of an engine body 2, a carburetor 3, an LPG regulator 4, an electronic control unit 5 (hereinafter referred to as an ECU), and the like.

The engine body 2 has a piston 7 in a cylinder block 6, and a combustion chamber 8 formed in the upper portion of the piston 7 has a structure in which an intake valve 9 is opened to take in an air-fuel mixture from an intake port. ing. Further, a water jacket 12 for circulating cooling water is formed in the cylinder block 6, and a water temperature sensor 13 for detecting the cooling water temperature is arranged.

The air-fuel mixture in the combustion chamber 8 burns when the ignition plug 10 ignites, drives the piston 7, and the generated combustion gas is discharged to the exhaust port by opening the exhaust valve 11. . An exhaust passage 16 and three-way catalysts 17 and 18 are connected to the exhaust port, and the combustion gas passes through the exhaust passage 16 and is purified by the three-way catalysts 17 and 18 before being discharged.

On the other hand, the intake port is connected to the intake passage 14, and the outside air is taken in from the intake passage 14. An air cleaner 15 is provided at the outside air intake end of the intake passage 14 so that dust contained in the outside air does not enter the combustion chamber 8. A carburetor 3 is integrally connected to an intermediate position of the intake passage 2.

The structure of the carburetor 3 will be described with reference to FIG. 2 in addition to FIG. FIG. 2 is an enlarged view of the carburetor 3. The carburetor 3 roughly includes a venturi 19, a throttle valve 20, an idle speed control bypass passage 21 (hereinafter referred to as ISC bypass passage), an idle speed control valve 22 (hereinafter referred to as ISCV), and a flow rate control valve 2.
3 and the like are integrally incorporated in the carburetor turbo 24.

Intake passage 14 in carburetor turbo 24
A venturi 19 is formed in the venturi 19, and the intake passage 14 is narrowed by the venturi 19.
Further, a throttle valve 20 that is opened / closed in conjunction with the operation of an accelerator pedal (not shown) is provided at a position downstream of the position where the venturi 19 is formed in the intake passage 14 with respect to the flow of air. The throttle valve 20 is opened and closed to adjust the intake air amount into the intake passage 14. In the vicinity of the throttle valve 20, when the throttle valve 20 is in the fully closed position, this is detected to detect the throttle fully closed signal ID.
A throttle sensor 25 for turning on the output of L is provided.

The ISC bypass passage 21 is provided so that the throttle valve 20 is bypassed.
Is a passage that connects the upstream side and the downstream side of the ISCV22. This ISCV2
Reference numeral 2 has a function of controlling the amount of intake air flowing through the ISC bypass passage 21 in the idle state where the throttle valve 20 is at the fully closed position, and preventing a decrease in idle speed due to, for example, an electric load and an air conditioner.

The flow control valve 23 is used for the stepping motor 2
6 and a needle valve 27. The flow rate control valve 23 is arranged at an intermediate position of a fuel passage 28 that connects the LPG regulator 4 and the venturi 19 described later, particularly at a position near the venturi 19.

As shown in FIG. 3, the stepping motor 26 has a rotor RT made of a laminated iron core inside, and has two layers and four poles of magnetic poles GK1, GK2 on the outer periphery of the rotor RT.
The magnetic pole GK1 is configured to have GK3 and GK4.
To the rotor R by switching the excitation voltage to GK4
Rotate T. This stepping motor 26 is an ECU
The battery 46 connected to the battery 5 is driven by a power source, and specifically, the battery 46 is driven in response to a drive control pulse signal (hereinafter referred to as a drive control signal) supplied from the ECU 5. . A gear mechanism (not shown) is provided inside the stepping motor 26, and is configured to convert the rotation of the rotor RT into the linear movement of the needle valve 27.

Grease is provided as a lubricant in the stepping motor 26 and the gear mechanism. The grease has a composition in which a thickener is uniformly dispersed in lubricating oil and has a predetermined viscosity. The viscosity of this grease changes with temperature, and the higher the temperature, the lower the viscosity.
It shows the characteristic that the viscosity becomes high when the temperature is low. As the viscosity increases, the rotor RT in the step motor 26 and the gear in the gear mechanism need to be driven against the viscous resistance of this grease. In the following description, the force acting on the rotor RT and the gear due to the viscous resistance of the grease is referred to as resistance force.

On the other hand, the tip of the needle valve 27 is tapered, and the needle valve 27 is formed in the carburetor turbo 24 so that the fuel passage 28 is bent into an L shape.
It is configured to face the bent portion of the. In particular,
A valve seat portion 29 is formed at a bent portion of a fuel passage 28 formed in the carburetor turbo 24 and the needle valve 2
7 is arranged to face the valve seat portion 29.

Therefore, the passage area of the fuel passage 28 can be varied by moving the needle valve 27 in the advancing / retreating direction (left-right direction in the drawing) by the stepping motor 26. As a result, the flow rate control valve 23 can control the flow rate of the fuel supplied from the LPG regulator 4, and the air-fuel ratio control is performed based on the oxygen concentration contained in the exhaust gas output by the O ₂ sensor 43 (described later). It becomes possible to do.

In this embodiment, the needle valve 27 advances in the valve closing direction (the direction indicated by the arrow X1 in FIG. 2) by the forward rotation of the stepping motor 26, and the needle valve 27 opens by the reverse rotation. It is configured to retreat in the direction (direction indicated by arrow X2 in FIG. 2).

In the above structure, the stepping motor 2
When the flow control valve 23 is opened by the reverse rotation of the valve 6, the fuel supplied from the LPG regulator 4 is supplied to the venturi 19 at a flow rate corresponding to the valve opening degree of the flow control valve 23, and the fuel is provided in the venturi 19. A slit 30
Fuel is supplied to the intake passage 14 from.

Further, a spring 26a is arranged between the needle valve 27 and the casing of the stepping motor 26. The spring 26a is configured to urge an elastic force in a direction of separating the needle valve 27 from the casing, and the elastic force prevents the backlash in the gear mechanism and the rattling of the needle valve 27 during operation. It is configured to do.

Therefore, when the needle valve 27 is opened (when the step motor 26 rotates in the reverse direction), the step motor 26 must open the needle valve 27 against the elastic force of the spring 26a. . In this case, the elastic force of the spring 26a is
Acts as a force (hereinafter, this force is also referred to as a resistance force) that hinders the driving of. On the contrary, when the needle valve 27 is closed (when the step motor 26 rotates forward), the elastic force of the spring 26a acts in a direction to help drive the step motor 26.

On the other hand, an air adjusting passage 31 is formed at a position opposed to the ISC bypass passage 21 of the carburetor turbo 24 so as to bypass the throttle valve 20. The air adjusting passage 31 is provided with an air adjusting screw 32 for adjusting the passage area. The air adjusting passage 31 and the air adjusting screw 32
Is provided to correct the flow rate of the ISC bypass passage 21 during idling.

Further, an injector mounting portion 34 to which an LPG injector 33 is mounted is formed below the position where the air adjusting passage 31 of the carburetor turbo 24 is formed (downstream of the throttle valve 20). This injector 33 has a correction fuel passage 35.
It is connected to the LPG regulator 4 via the engine, and is configured to inject fuel for air-fuel ratio correction toward the intake passage 14, particularly during light load operation. As a result, the air-fuel ratio is stabilized during engine operation.

The LPG regulator 4 includes a fuel tank 37.
It has a function of vaporizing the liquid fuel stored in the venturi 19 and supplying it to the venturi 19 at a predetermined pressure. This LPG
The regulator 4 has a first decompression chamber (not shown) and a second decompression chamber (not shown) therein. The first decompression chamber is connected to the fuel tank 37 via the tank-side fuel passage 36, and The second decompression chamber is connected to the venturi 19 via the fuel passage 28 described above. A main solenoid valve 38 that shuts off the supply of fuel from the fuel tank 37 to the LPG regulator 4 is provided in the middle of the tank-side fuel passage 36.

Liquid fuel is supplied from the fuel tank 37 to the first pressure reducing chamber of the LPG regulator 4, and the liquid fuel is depressurized and vaporized in the first pressure reducing chamber. Further, since the second decompression chamber is connected to the venturi 19, when the LPG engine 1 is started and the venturi negative pressure acts on the second decompression chamber, the second decompression chamber is separated between the first decompression chamber and the second decompression chamber. The ilastic valve provided in is opened and the fuel in the first decompression chamber is introduced into the second decompression chamber.

As a result, the vaporized fuel introduced into the second pressure reducing chamber is supplied to the venturi 19 via the fuel passage 28. Further, when the Venturi negative pressure becomes small and becomes close to the atmospheric pressure, the above-mentioned ilastic valve is closed and the fuel supply from the first pressure reducing chamber to the second pressure reducing chamber is stopped. As a result, the fuel in the second decompression chamber maintains a substantially atmospheric pressure.

The auxiliary fuel passage 35 connected to the injector 33 is connected to the first pressure reducing chamber of the LPG regulator 4, and the flow rate of the fuel flowing through the slow fuel passage 35a is controlled at the connecting position. A slow lock solenoid valve 39 is provided. The slow lock solenoid valve 39 is configured to be opened except during normal traveling deceleration. Therefore, as described above, the injector 33 is opened during valve opening.
Fuel is injected toward the intake passage 14 from.

On the other hand, the ISCV 22, the stepping motor 26, the injector 33, the main solenoid valve 38, and the slow lock solenoid valve 39 are connected to the ECU 5 and their drives are controlled. Further, the ECU 5 includes the water temperature sensor 13,
The throttle sensor 25 is connected, and the pressure sensor 40, the rotation speed sensor 41, the vehicle speed sensor 42, the O ₂ sensor 43, the battery sensor 45, etc. are connected. Furthermore,
A battery 46 serving as a power source is connected to the ECU 5.

The pressure sensor 40 detects the pressure in the intake passage 14, and is arranged downstream of the throttle valve 20 in the intake passage 14. The rotation speed sensor 41 detects the engine rotation speed (engine rotation speed) and is attached to the distributor 44.
The vehicle speed sensor 42 detects the vehicle speed of the vehicle in which the LPG engine 1 is mounted, and is configured to detect the vehicle speed by detecting the rotation of the speedometer cable, for example. Further, the O ₂ sensor 43 detects the oxygen concentration in the exhaust gas, and is attached to the exhaust passage 16. Further, the battery sensor 45 is configured to detect the voltage of the battery 46.

The ECU 5 uses the sensors 13 and 2 described above.
The ISCV 22, the stepping motor 26, the injector 33, the main solenoid valve 38, the slow lock solenoid valve 39, etc. are suitably controlled in accordance with the output signals output from 5, 40 to 43, 45 so as to correspond to the operating state.

Next, the hardware configuration of the ECU 5 will be described. FIG. 4 is a block diagram showing the hardware configuration of the ECU 5. The ECU 5 is a well-known central processing unit (CPU) 5
1, a read-only memory (ROM) 52, a random access memory (RAM) 53, a backup RAM 54 for storing stored data, and the like, and these are connected to an external input circuit 55, an external output circuit 56, and the like by a bus 57. Configured as a logical operation circuit.

The water temperature sensor 13, the throttle sensor 25, the pressure sensor 40, the rotation speed sensor 41, the vehicle speed sensor 42, the O ₂ sensor 43, the battery sensor 45, etc. are connected to the external input circuit 55. Through the input circuit 55, the CPU 51 reads the signal output from each sensor or the like as an input value. Based on these input values, the CPU 51 connects the above-mentioned I connected to the external output circuit 57.
SCV22, stepping motor 26, injector 3
3, the main solenoid valve 38, the slow lock solenoid valve 39 and the like are controlled.

The ROM 52 of the ECU 5 stores in advance a step motor drive control processing program, a predetermined value used for the step motor drive control processing, and the like, which will be described below. Further, the ECU 5 has a timer 58 for measuring the time, and a conveyor register for outputting an interrupt signal to the CPU 51 is also arranged in the external output circuit 56 when a preset time coincides with the time measured by the timer 58. It is set up.

In the above structure, the step motor drive control device, which is the main part of the present invention, is composed of the ECU 5, the step motor 26, the water temperature sensor 13, the battery sensor 45, the battery 46 and the like. The operation of the step motor drive control device composed of these components will be described below.

The step motor drive control device according to this embodiment is configured to control the drive of the step motor 26 in accordance with a step motor drive control processing program executed by the ECU 5. FIG. 5 is a flowchart showing a step motor drive control processing program executed by the ECU 5.

Prior to the description of the step motor drive control process shown in FIG. 5, the basic principle of the drive control process of the step motor 26 in this embodiment will be described with reference to FIGS. 6 to 10. As described above, the step motor 26 is configured to be driven by using the battery 46 connected to the ECU 5 as a power source, and is specifically configured to be driven in response to the drive control signal supplied from the ECU 5. . However, the driving force of the step motor 26 changes depending on the voltage of the battery 46 serving as a power source. FIG.
The driving force of the step motor 26 and the voltage of the battery 46 (B
(AT)).

As shown in the figure, the battery voltage BA
If T is small, the magnetic poles GK1 to GK4 of the step motor 26
The magnetic force generated (see FIG. 3) becomes small, and therefore the driving force of the step motor 26 also becomes small. As shown in FIG. 6, the driving force of the step motor 26 has a characteristic that it increases as the battery voltage BAT increases.

Therefore, when the drive control signal having a high drive frequency is supplied from the ECU 5 in the state where the battery voltage BAT is small, that is, the drive force is small, the step motor 26 can be driven following the drive control signal. As described above, the loss of synchronization and the occurrence of step-out occur. For this reason, the step motor drive control device according to the present embodiment, similarly to the device having the conventional configuration, sets the upper limit value of the drive frequency at which the step motor 26 can perform the drive following the drive control signal in accordance with the value of the battery voltage BAT. By setting the drive frequency of the drive control signal supplied from the ECU 5 so as not to exceed the upper limit value, the step motor 26 is configured so that step-out does not occur.

By the way, the cause of the step-out occurring in the step motor 26 exists in addition to the above-mentioned decrease of the battery voltage BAT. Specifically, it is also generated by the viscous force of grease arranged inside the step motor 26 and the gear mechanism and the elastic force of the spring 26a arranged between the needle valve 27 and the casing of the stepping motor 26. . The individual causes will be considered below.

FIG. 7 shows the relationship between the environmental temperature in which the step motor 26 and the gear mechanism are arranged and the viscous force (resistive force) of the grease. In this embodiment, the step motor 2
6, a water temperature sensor 13 is used as a means for detecting the environmental temperature in which the gear mechanism is disposed, and the above-mentioned environmental temperature is estimated by the cooling water temperature (THW) of the LPG engine 1 detected by the water temperature sensor 13. I am trying.

Since the carburetor 3 in which the step motor 26 is installed is directly installed in the engine body 2, the carburetor 3 is installed depending on the cooling water temperature (THW).
Even if the environment temperature in which the gear mechanism is arranged is estimated, there is no particular problem. It is also possible to use another temperature sensor or a grease temperature sensor that directly detects the temperature of the grease.

As shown in FIG. 7, the cooling water temperature THW
When is low, the temperature of the grease is low, and the viscous force (resisting force) of the grease is large. Further, the viscous force (resistive force) of the grease exhibits a characteristic that it decreases as the cooling water temperature increases. Therefore, when the drive control signal of a high drive frequency is supplied from the ECU 5 in a state where the viscous force (resistive force) of the grease is large, the step motor 26
Cannot be driven following the drive control signal, and there is a possibility that step-out will occur.

Therefore, the upper limit value of the drive frequency is set to a low frequency that allows the step motor 26 to drive in accordance with the drive control signal in accordance with the value of the cooling water temperature THW.
By configuring the drive frequency of the drive control signal supplied from No. 5 so as not to exceed the upper limit value, the occurrence of step-out caused by the viscous force (resistive force) of grease acting on the step motor 26 is prevented. be able to.

However, if the upper limit of the drive frequency is fixed to a value corresponding to the low cooling water temperature and cannot be varied, if the cooling water temperature THW rises and the viscous force (resisting force) of the grease decreases, the step motor 26 Is in a state where it can be driven at a high driving frequency, but the upper limit of the driving frequency is set to a low value corresponding to a low temperature, so that it becomes impossible to drive the step motor 26 with good responsiveness. .

Therefore, the upper limit value of the drive frequency can be varied according to the change of the cooling water temperature THW, and the upper limit of the drive frequency can be obtained when the viscosity of the grease is large (that is, the cooling water temperature THW is low). The value is set low, and when the viscosity of grease is small (that is, when the cooling water temperature THW is high), the upper limit of the drive frequency is set high to prevent out-of-step at low temperature and to respond at high temperature. It is possible to realize the improvement of sex together.

Next, the elastic force of the spring 26a will be focused on and explained below. FIG. 8 shows the relationship between the amount of displacement of the needle valve 27 that is displaced in the forward / backward direction by the step motor 26 and the elastic force (resistance force) generated by the spring 26a. In the figure, the horizontal axis indicates the displacement amount of the needle valve 27, and the displacement amount when the step motor 26 is rotating normally (that is, when the needle valve 27 is moving in the valve closing direction) is shown to the right of the zero point. The displacement amount when the step motor 26 is rotating in the reverse direction (that is, when the needle valve 27 is moving in the valve closing direction) is shown on the left side of the zero point. Also, in the figure, the vertical axis represents the elastic force of the spring 26a.

As shown in the figure, the spring 26a
The elastic force of is always a constant value regardless of the rotation direction of the step motor 26. However, when the needle valve 27 is opened (displaced in the arrow X2 direction) as described above, the displacement direction of the needle valve 27 and the spring 2
Since the urging direction of the elastic force of 6a is opposite, the step motor 26 needs to open the needle valve 27 against the elastic force of the spring 26a. Therefore, when the step motor 26 rotates in the reverse rotation direction (load increase direction), the elastic force of the spring 26 a acts as a resistance force that hinders the driving of the step motor 26.

On the contrary, when the needle valve 27 is closed (displaced in the direction of arrow X1), the needle valve 2
Since the displacement direction of 7 and the urging direction of the elastic force by the spring 26a are the same direction, the elastic force of the spring 26a acts in a direction to assist the driving of the step motor 26.

Therefore, when the step motor 26 reversely rotates (when the load increases), the elastic force of the spring 26a acts as a resistance force that hinders the driving of the step motor 26.
When the drive control signal having a high drive frequency is supplied from the CU 5, the step motor 26 cannot be driven following the drive control signal, and there is a possibility that step-out may occur. Therefore, when the step motor 26 is rotating in the reverse direction, the upper limit value of the drive frequency is set to a low frequency at which the step motor 26 can be driven following the drive control signal.
The drive frequency of the drive control signal supplied from the step motor 2 is configured so as not to exceed the upper limit value.
6, it is possible to prevent the occurrence of step-out due to the elastic force of the spring 26a.

However, if the upper limit of the drive frequency is fixed to a value corresponding to the reverse rotation of the step motor 26 and cannot be varied, the step motor 26 rotates in the forward rotation direction (reduction load direction) and the elastic force of the spring 26a is increased. Even when the step motor 26 acts to help drive the step motor 26, the upper limit of the drive frequency is set to a low value corresponding to the reverse rotation, so that the step motor 26 having a high responsiveness cannot be driven. .

Therefore, the upper limit value of the drive frequency can be varied according to the rotation direction of the step motor 26, and the elastic force of the spring 26a acts as a resistance force during the load increasing direction rotation (that is, during the reverse rotation). In this case, the upper limit value of the drive frequency is set low, and the upper limit value of the drive frequency is set high during the rotation in the unloading direction in which the elastic force of the spring 26a acts as an auxiliary force (that is, in the normal rotation), the reverse rotation is performed. It is possible to realize both the prevention of step-out at the time and the improvement of the responsiveness at the time of forward rotation.

FIG. 9 shows the battery voltage BAT, the cooling water temperature THW, and the step motor 26, which are parameters for setting the upper limit value of the driving frequency based on the above-described principle.
The result of obtaining the upper limit value of the optimum drive frequency is shown according to the rotation direction. In the same figure, the horizontal axis represents the battery voltage BAT, and the vertical axis represents the upper limit value of the drive frequency. Further, as the cooling water temperature THW, T1 to T3 are shown as an example, and the case where the step motor 26 is rotating in the reverse direction is indicated by a solid line in the figure, and the case where the step motor 26 is rotating in the forward direction is indicated by a broken line in the figure. It shows with.

As shown in the figure, the battery voltage BA
The lower T is, the lower the upper limit value of the drive frequency is, and the characteristic is that the upper limit value of the drive frequency increases as the battery voltage BAT increases. Also, the cooling water temperature TH
The lower the W is, the lower the upper limit of the drive frequency is, and the upper limit of the drive frequency is increased as the cooling water temperature THW is increased. Furthermore, step motor 2
The upper limit of the drive frequency is lower in the reverse rotation (when the valve is open) than in the normal rotation (when the valve is closed) of No. 6.

Therefore, the battery voltage BAT, the cooling water temperature THW, and the rotation direction of the step motor 26 are respectively detected, the upper limit of the drive frequency is set from FIG. 9 based on the detected values, and the set drive frequency is set. By performing the drive control of the step motor 26 by the upper limit value of, it is possible to prevent the out-of-step and improve the responsiveness during the drive control of the step motor 26.

FIGS. 10A and 10B show maps used in the step motor drive control process shown in FIG.
It is set based on the upper limit value of the optimized driving frequency shown in FIG. FIG. 10 (A) is a map when the step motor 26 rotates forward, and FIG. 10 (B) is a map when the step motor 26 rotates backward. In addition, each map value SOP _XY, SCL shown in the figure
_XY (X and Y are integers. X = 1 to 3 and Y = 1 to 3) has characteristics substantially like the following equations by corresponding to FIG.

SOP _1-Y ≤ SOP _2-Y ≤ SOP _3-Y (Y is constant) (1) SOP _X-1 ≤ SOP _X-2 ≤ SOP _X-3 (X is constant) ...... (2 ) SCL _1-Y ≤ SCL _2-Y ≤ SCL _3-Y (Y is constant) (3) SCL _X-1 ≤ SCL _X-2 ≤ SCL _X-3 (X is constant) ...... (4) Continued Then, the step motor drive control processing executed based on the basic principle of the drive control processing of the step motor 26 described above will be described with reference to FIG. The step motor drive control processing routine shown in the figure is executed by a regular interrupt every predetermined time.

When the step motor drive control process is started, the process of step 100 is first performed. This step 1
00 and step 102 are performed by the step motor 26
Is a process for detecting the rotation direction of the above, and serves as the drive direction determining means described in the above claims. In step 100, a step difference SA (SA = S−) between the step number S of the step motor 26 and the previous step number S ₀ of the step motor 26 at the time of the routine processing of this time.
Calculate S ₀ ).

Here, when the step difference SA is a positive value (SA> 0), the step number S at this time is larger than the step number S at the previous time. Therefore, the step motor 26 is normally rotated. It can be determined that vice versa,
When the step difference SA is a negative value (SA <0), it means that the step number S at this time is smaller than the step number S at the previous time. Therefore, it can be determined that the step motor 26 is rotating in the reverse direction. it can. Further, when the step difference SA is zero (SA = 0), it means that the step number S at this time is equal to the step number S at the previous time, so that it can be determined that the step motor 26 is stopped. it can. Therefore, in step 102, based on the step difference SA calculated in step 100, the step motor 26
Determine the rotation direction of. Although not shown, in order to prepare for the next routine process, the previous step number S ₀ is updated to the current step number S (S ₀ ← S) after performing the process of step 102.

By the processing of step 102, the step motor 26 is rotating in the normal direction (that is, the valve closing operation).
If it is determined that the step motor 26 is rotating in the reverse direction (that is, the valve opening operation is performed), the process proceeds to step 104.
Go to 30. Further, in step 102, the step motor 2
If it is determined that No. 6 is stopped, it is not necessary to set the upper limit value of the drive frequency, and this routine is ended.

As described above, when it is determined that the step motor 26 is rotating in the normal direction, the process for setting the upper limit value of the drive frequency during the normal rotation shown in steps 104 to 128 is executed. First, step 104
Then, the environmental temperature in which the step motor 26 and the gear mechanism are arranged is estimated based on the cooling water temperature THW detected by the water temperature sensor 13 functioning as a temperature detecting means. As described above, in the present embodiment, the water temperature sensor 13 is used as a means for detecting the environmental temperature in which the step motor 26 and the gear mechanism are arranged, but other temperature sensors may be used.

Further, in the present embodiment, as shown in FIG. 10, the cooling water temperature THW is 3 when the temperature is low (THW <T1), when the temperature is intermediate (T1≤THW <T2), and when the temperature is high (THW≥T2).
The configuration is such that the upper limit of the drive frequency is set by dividing into regions (however, T1 <T2). And step 104
When it is determined that the cooling water temperature THW is low temperature (THW <T1), the process proceeds to step 106, where the battery voltage BAT of the battery 46 is determined based on the detection result of the battery sensor 45 functioning as a voltage detecting means. judge. In the present embodiment, as shown in FIG. 10, the battery voltage BAT is low (BAT <V1) and intermediate (V).
The configuration is such that the upper limit value of the driving frequency is set by dividing into three regions of 1≤BAT <V2) and high voltage (BAT≥V2) (however, V1 <V2).

If it is determined in step 106 that the battery voltage BAT is low (BAT <V1), the process proceeds to step 108, and FIG.
SOP _1-1 is set as the upper limit value (X) of the drive frequency based on the map shown in (X ← SOP _1-1 ). When it is determined in step 106 that the battery voltage BAT is at the intermediate voltage (V1 ≦ BAT <V2), the process proceeds to step 110, and the drive frequency upper limit is set based on the map shown in FIG. setting the SOP _{1- 2} as the value X (X ← SOP _1-2). Further, when it is determined in step 106 that the battery voltage BAT is at the high voltage (BAT ≧ V2), the process proceeds to step 112, and the upper limit value X of the drive frequency is set based on the map shown in FIG. Set SOP _1-3 as (X ← SOP _1-3 ).

On the other hand, when it is determined in step 104 that the cooling water temperature THW is the intermediate temperature (T1≤THW <T2), the process proceeds to step 114, where the detection result of the battery sensor 45 functioning as voltage detecting means is detected. Based on, the battery voltage BAT of the battery 46 is determined. Then, when it is determined in step 114 that the battery voltage BAT is the low voltage (BAT <V1), the process proceeds to step 116, and the upper limit value X of the drive frequency is set based on the map shown in FIG. SOP _2-1 is set as (X ← SOP _2-1 ). In step 114, when the battery voltage BAT is the intermediate voltage (V1 ≦ BAT <
If it is determined to be V2), the process proceeds to step 118, and SOP _2-2 is set as the upper limit value X of the drive frequency based on the map shown in FIG. 10 (A) (X ← SOP
_2-2 ). Furthermore, when it is determined in step 114 that the battery voltage BAT is at the high voltage (BAT ≧ V2), the process proceeds to step 120, and the upper limit value X of the drive frequency is set based on the map shown in FIG. As SOP
Set _2-3 (X ← SOP _2-3 ). When the upper limit X of the drive frequency is set in each of steps 108 to 112, steps 116 to 120, and steps 124 to 128 as described above, the step motor drive control process ends.

On the other hand, when it is determined in step 104 that the cooling water temperature THW is at a high temperature (THW ≧ T2), the process proceeds to step 122, and based on the detection result of the battery sensor 45 functioning as voltage detecting means, The battery voltage BAT of the battery 46 is determined. Then, when it is determined in step 122 that the battery voltage BAT is the low voltage (BAT <V1), the process proceeds to step 124, and the upper limit value X of the drive frequency is set based on the map shown in FIG. Set SOP _3-1 as (X
← SOP _3-1 ). When it is determined in step 122 that the battery voltage BAT is at the intermediate voltage (V1 ≦ BAT <V2), the process proceeds to step 126, and the upper limit of the drive frequency is set based on the map shown in FIG. SOP _3-2 is set as the value X (X ← SOP _3-2 ). Further, when it is determined in step 122 that the battery voltage BAT is high voltage (BAT ≧ V2), the process proceeds to step 128, and the upper limit value X of the drive frequency is set based on the map shown in FIG. SOP _3-3 is set as (X ← SOP _3-3 ).

Steps 104 to 128 described above
The upper limit value X of the driving frequency is calculated as shown in FIG.
It is set to a value corresponding to the map value shown in. Further, the map value shown in FIG. 10A is an optimum value adapted to the parameters of the battery voltage BAT, the cooling water temperature THW, and the rotation direction of the step motor 26 shown in FIG. Therefore, even if the viscosity of the grease arranged in the step motor 26 and the gear mechanism changes with the change of the environmental temperature, or even if the driving force of the step motor 16 changes with the change of the battery voltage BAT,
It is possible to set the upper limit value of the drive frequency adapted to the battery voltage BAT and the cooling water temperature THW.

The processing of steps 104 to 128 is the processing executed when it is determined in step 102 that the step motor 26 is rotating normally, and as shown by the broken line in FIG. The upper limit of the drive frequency set when the motor 26 is rotating normally is set higher than the upper limit of the drive frequency (shown by the solid line in FIG. 9) set when the step motor 26 is rotating in the reverse direction. To be done. As described above, when the step motor 26 is driven, the upper limit of the drive frequency is set high in the normal rotation state in which the elastic force of the spring 26a acts as an auxiliary force, so that the responsiveness of the step motor 26 is particularly improved. You can

Then, in the processing of step 102,
A process executed when it is determined that the step motor 16 is rotating in the reverse direction (that is, the valve opening operation is performed) will be described. When it is determined in step 102 that the step motor 26 is rotating normally, the setting processing of the upper limit value of the driving frequency during reverse rotation shown in steps 130 to 154 is executed.

First, at step 130, the cooling water temperature TH detected by the water temperature sensor 13 functioning as a temperature detecting means.
Based on W, the environmental temperature in which the step motor 26 and the gear mechanism are arranged is estimated. When it is determined in step 130 that the cooling water temperature THW is low (THW <T1), the process proceeds to step 132, where the battery 46 of the battery 46 is detected based on the detection result of the battery sensor 45 functioning as a voltage detecting means. Determine the battery voltage BAT.

When it is determined in step 132 that the battery voltage BAT is low (BAT <V1), the process proceeds to step 134, and FIG.
S as the upper limit value X of the driving frequency based on the map shown in
Set CL _1-1 (X ← SCL _1-1 ). If it is determined in step 132 that the battery voltage BAT is the intermediate voltage (V1 ≦ BAT <V2), the process proceeds to step 136, and the upper limit of the drive frequency is set based on the map shown in FIG. 10 (B). Set SCL _1-2 as the value X (X ← SCL _1-2 ). Further, when it is determined in step 132 that the battery voltage BAT is high voltage (BAT ≧ V2), the process proceeds to step 138, and the upper limit value X of the drive frequency is set based on the map shown in FIG. Set SCL _1-3 as (X ← SCL _1-3 ).

On the other hand, when it is determined in step 130 that the cooling water temperature THW is the intermediate temperature (T1≤THW <T2), the process proceeds to step 140, where the detection result of the battery sensor 45 functioning as voltage detecting means is detected. Based on, the battery voltage BAT of the battery 46 is determined. Then, when it is determined in step 140 that the battery voltage BAT is the low voltage (BAT <V1), the process proceeds to step 142, and the upper limit value X of the drive frequency is set based on the map shown in FIG. SCL _2-1 is set as (X ← SCL _2-1 ). In step 140, when the battery voltage BAT is the intermediate voltage (V1 ≦ BAT <
If it is determined to be V2), the process proceeds to step 144, and SCL _2-2 is set as the upper limit value X of the drive frequency based on the map shown in FIG. 10B (X ← SCL
_2-2 ). Further, when it is determined in step 140 that the battery voltage BAT is high voltage (BAT ≧ V2), the process proceeds to step 146, and the upper limit value X of the drive frequency is set based on the map shown in FIG. As SCL
Set _2-3 (X ← SCL _2-3 ).

On the other hand, when it is determined in step 130 that the cooling water temperature THW is high temperature (THW ≧ T2), the process proceeds to step 148, where the detection result of the battery sensor 45 functioning as the voltage detecting means is determined. The battery voltage BAT of the battery 46 is determined. Then, when it is determined in step 148 that the battery voltage BAT is the low voltage (BAT <V1), the process proceeds to step 150, and the upper limit value X of the drive frequency is set based on the map shown in FIG. 10 (B). Set SCL _3-1 as (X
← SCL _3-1 ). If it is determined in step 148 that the battery voltage BAT is the intermediate voltage (V1 ≦ BAT <V2), the process proceeds to step 152, and the upper limit of the drive frequency is set based on the map shown in FIG. 10 (B). Set SCL _3-2 as the value X (X ← SCL _3-2 ). Further, when it is determined in step 148 that the battery voltage BAT is high voltage (BAT ≧ V2), the process proceeds to step 154, and the upper limit value X of the drive frequency is set based on the map shown in FIG. 10 (B). Set SCL _3-3 as (X ← SCL _3-3 ). As described above, steps 134 to
138, steps 142-146, steps 150-1
When the upper limit value X of the drive frequency is set in each step of 54, the step motor drive control process ends.

Steps 130 to 154 described above
The upper limit value X of the driving frequency is calculated by the process of FIG.
It is set to a value corresponding to the map value shown in. Further, the map value shown in FIG. 10 (B) is an optimum value adapted to the parameters of the battery voltage BAT, the cooling water temperature THW, and the rotation direction of the step motor 26 shown in FIG. Therefore, even if the viscosity of the grease arranged in the step motor 26 and the gear mechanism changes with the change of the environmental temperature, or even if the driving force of the step motor 16 changes with the change of the battery voltage BAT,
It is possible to set the upper limit value of the drive frequency adapted to the battery voltage BAT and the cooling water temperature THW.

The processing of steps 130 to 154 is the processing executed when it is determined in step 102 that the step motor 26 is rotating in the reverse direction, and as shown by the solid line in FIG. The upper limit of the drive frequency set when the motor 26 is rotating in the reverse direction is set lower than the upper limit of the drive frequency (shown by the broken line in FIG. 9) set when the step motor 26 is rotating in the forward direction. To be done. As described above, when the step motor 26 is driven, it is possible to prevent step-out of the step motor 26 by setting the upper limit value of the drive frequency low in the reverse rotation state in which the elastic force of the spring 26a acts as a resistance force. Can be prevented.

As described above, by executing the step motor drive control process shown in FIG. 5, it is possible to effectively prevent the occurrence of step-out when driving the step motor 26, and to improve the responsiveness. be able to. still,
In the step motor drive control process shown in FIG. 5, the processes of steps 104 to 128 and the processes of steps 130 to 154 are the drive frequency setting means described in the claims.

In this embodiment, the engine is taken as an example of the application of the step motor drive control device, and the battery voltage BAT, the cooling water temperature THW, and the rotation of the step motor 26 are used as parameters for setting the upper limit value of the drive frequency. A configuration using three parameters of direction is adopted. However, the device to which the step motor 26 is applied
When there is another parameter that causes the step motor 26 to generate step-out according to the characteristics of the device, the upper limit value of the drive frequency may be set by adding the other parameter.

[0093]

As described above, according to the present invention, various effects described below can be realized. According to the first and third aspects of the present invention, it is possible to effectively prevent the occurrence of step-out when driving the step motor, and it is possible to perform drive control of the step motor with good responsiveness.

According to the inventions of claims 2 and 4, in addition to the effects of the inventions of claims 1 and 3 described above,
It is possible to improve the responsiveness when the step motor rotates in the direction of decreasing the load, and it is possible to prevent the occurrence of step-out when the step motor rotates in the direction of increasing the load.

Further, in the inventions according to claims 3 and 4, the increase / decrease control of the fuel supply can be carried out promptly and with high accuracy, and the reliability of the engine control can be improved.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of an LPG engine to which a fuel control device according to a first embodiment of the present invention is applied.

FIG. 2 is an enlarged sectional view showing a carburetor.

FIG. 3 is a schematic configuration diagram of a stepping motor.

FIG. 4 is a block diagram showing a configuration of an ECU.

FIG. 5 is a flowchart showing a step motor drive control process.

FIG. 6 is a diagram showing a relationship between a battery voltage BAT and a driving force of a step motor.

FIG. 7 is a diagram showing a relationship between a cooling water temperature THW and a viscous force (resisting force) of grease.

FIG. 8 is a diagram showing a relationship between a displacement amount of a needle valve and an elastic force generated by a spring.

FIG. 9 is a diagram showing a relationship between a battery voltage, a cooling water temperature, and an upper limit value of a driving frequency.

FIG. 10A is a diagram showing a map for obtaining an upper limit value of a drive frequency when the step motor rotates in the normal direction,
(B) is a diagram showing a map for obtaining the upper limit value of the drive frequency when the step motor rotates in the reverse direction.

[Explanation of symbols]

 1 LPG Engine 2 Engine Body 3 Carburetor 4 LPG Regulator 5 ECU 13 Water Temperature Sensor 14 Intake Passage 16 Exhaust Passage 19 Venturi 20 Throttle Valve 21 ISC Bypass Passage 22 ISCV 23 Flow Control Valve 25 Throttle Sensor 26 Stepping Motor 26a Spring 27 Needle Valve 28 Fuel passage 29 Valve seat portion 30 Slit 33 Injector 35 Auxiliary fuel passage 36 Tank side fuel passage 37 Fuel tank 38 Main solenoid valve 39 Slow lock solenoid valve 40 Pressure sensor 41 Rotation speed sensor 42 Vehicle speed sensor 45 Battery sensor 46 Battery 51 CPU 52 ROM 53 RAM

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location F02D 45/00 378 F02D 45/00 378 F02M 21/02 F02M 21/02 L 21/04 21/04 F H02P 8/12 H02P 8/00 K 8/38 R

Claims (4)

[Claims] 1. A step motor drive control device for driving and controlling a step motor for driving an engine control means, a voltage detection means for detecting a voltage of a drive power source, a temperature detection means for detecting a temperature state, and the voltage detection means. And based on the detection result of the temperature detection means,
A stepping motor drive control device, comprising: driving frequency setting means for setting an upper limit value of the stepping motor driving frequency. 2. A step motor drive control device for driving and controlling a step motor driven as engine control means, a voltage detection means for detecting a voltage of a drive power source, a temperature detection means for detecting a temperature state, and a step motor for the step motor. A drive direction determination means for determining a drive direction, and an upper limit value of a step motor drive frequency when the step motor is driven in a direction in which the drive resistance is small, based on the voltage value and the temperature value. Drive frequency setting means, and a second drive frequency setting for obtaining and setting an upper limit value of the step motor drive frequency when the step motor is driven in the direction in which the drive resistance is large, based on the voltage value and the temperature value. Means and an upper limit value set by the first drive frequency setting means based on the detection result of the drive direction determining means, or Second
And a selecting means for selecting the upper limit value set by the driving frequency setting means. 3. A step motor drive control device for controlling an amount of fuel supplied to an engine by a drive amount of a step motor, voltage detection means for detecting a battery voltage, and temperature detection means for detecting a temperature state of the engine. , Based on the detection result of the voltage detection means and the temperature detection means,
A stepping motor drive control device, comprising: driving frequency setting means for setting an upper limit value of the stepping motor driving frequency. 4. A step motor drive control device for controlling an amount of fuel supplied to an engine by a drive amount of a step motor, voltage detection means for detecting a battery voltage, temperature detection means for detecting a temperature state of the engine, Based on the detection result of the drive direction determination means for determining the drive direction of the step motor, the voltage detection means and the temperature detection means,
Drive frequency setting means for setting an upper limit value of the step motor drive frequency, the drive frequency setting means, based on the determination result of the drive direction determination means, the step motor in the reduction load direction with a small drive resistance. When the step motor is driven, the upper limit value of the step motor drive frequency is set to be large, and when the step motor is driven in the increasing load direction in which the drive resistance is large, the upper limit value of the step motor drive frequency is set to the deloading value. The step motor drive control device is characterized in that the step motor drive control device is set to be smaller than when driven in the direction.